Elite: Dangerous has been released as full game but due to time needed to do everything they wanted, some of the content is split into seasons.
Elite: Dangerous v1.x consists of full galaxy with billions of star systems, procedurally generated where every star system has few space stations (think there are four different types of stations). Space is modeled with close to scientific precision (only "game" that has better space model is Space Engine) but you can't land on celestial objects, only on stations and refueling platforms. Gameplay consist of trading (mostly) which is why game is known as Euro Truck Simulator in Space. Other prominent profession is bounty hunting (or riskier form of it, piracy), there is also exploration and mining but those are less popular among players. Maximum number of players in one instance is 32, but due to billions of star systems players are scattered all around the galaxy so you'll mostly deal with AI ships which are of decent quality. There is clan system called Wings and if you get some friends you'll be able to play with them and participate in supremacy mode called Powerplay where people fight for factions, solo or as part of Wings. There are actual battles between Wings, which is like clan match in cRPG. Current price of Elite is 15 USD, 12.5 EUR or 10 GBP.
Season One is known as Elite Horizons and should come out before end of this year. It will cost 50 EUR but owners of original game (v1.0) get a discount (15 USD or 12.5 EUR) which means it will cost you 37.5 EUR. Think of it as your typical season where you'll get updates for Horizons during whole year. Horizons will add planetary landings (somewhat seamless) and fights on planets. First version will feature moons and stations on those moons which you'll be able to explore with your ship or with SRV (surface reason vehicle) which is basically a space buggy. There will be buggy racing and buggies also have weapons and can be customized in same fashion as ships. Later patches will add bigger planets with foliages and life.
Season Two (late 2016) will bring final puzzle to the game, character customization and first person gameplay. You'll be able to get out of your seat and walk inside the ship and visit planets on foot, engage in various activities (big game hunting has been mentioned). This expansion or season pass will cost another 50 EUR.